U.S. patent application number 12/548412 was filed with the patent office on 2010-03-04 for expandable laminoplasty fixation system.
Invention is credited to Sohaib Kureshi, Brian McGuire.
Application Number | 20100057127 12/548412 |
Document ID | / |
Family ID | 41726501 |
Filed Date | 2010-03-04 |
United States Patent
Application |
20100057127 |
Kind Code |
A1 |
McGuire; Brian ; et
al. |
March 4, 2010 |
Expandable Laminoplasty Fixation System
Abstract
The present invention relates to a medical implant for bone
surgery, and more specifically to a vertebral fixation system with
an expandable configuration. Such implants are particularly useful
for securing and expanding transected spinal vertebrae following
laminoplasty procedures.
Inventors: |
McGuire; Brian; (Carlsbad,
CA) ; Kureshi; Sohaib; (Solana Beach, CA) |
Correspondence
Address: |
G. L. LOOMIS & ASSOCIATES, INC.
990 HIGHLAND DRIVE, SUITE 212Q
SOLANA BEACH
CA
92075
US
|
Family ID: |
41726501 |
Appl. No.: |
12/548412 |
Filed: |
August 26, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61091944 |
Aug 26, 2008 |
|
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Current U.S.
Class: |
606/246 ;
606/70 |
Current CPC
Class: |
A61B 17/8009 20130101;
A61B 17/7071 20130101; A61B 17/8023 20130101 |
Class at
Publication: |
606/246 ;
606/70 |
International
Class: |
A61B 17/70 20060101
A61B017/70; A61B 17/80 20060101 A61B017/80 |
Claims
1. A bone fixation device for the lamina of the spine after
laminoplasty comprising: an elongated fixation plate having
adjustable length comprising a first plate component having a
distal end, a proximal end and a longitudinal axis extending there
between; said first plate component being slidebly coupled to a
second plate component having a distal end, a proximal end and a
longitudinal axis extending there between; wherein the distal end
of the first plate component is configured to be fixedly attachable
to a lamina facet on one side of a transected lamina and wherein
the distal end of the second plate component is configured to be
fixedly attachable to a lamina facet on the side of the transected
lamina opposite the side to which the distal end of the first
component is fixedly attachable; wherein the first plate component
and second plate component can be slidably adjusted to produce a
desired overall fixation plate length while the distal ends of the
first and second plate components are each fixedly attached to
opposing facets of the transected lamina and the two plate
components are the locked relative to one another in the desired
positions; and a locking means to secure the position of the first
plate component and second plate component relative to one
another.
2. The bone fixation device of claim 1 wherein the distal end of
the first plate component and the distal end of the second plate
component each comprise one or more bone screw receiving holes
configured to permit fixed attachment to lamina facets with bone
screws.
3. The bone fixation device of claim 1 wherein said one or more
bone screw receiving holes is an elongated slot.
4. The bone fixation device of claim 1 wherein the locking means
comprises a setscrew.
5. The bone fixation device of claim 1 wherein the locking means
comprises a ratchet mechanism.
6. The bone fixation device of claim 1 wherein the proximal end of
the first plate component is slidably coupled within a pocket in
the proximal end of the second plate component.
7. The bone fixation device of claim 5 wherein the locking means
comprises a ratchet mechanism comprising a series of tooth-like
protrusions set an angle less of than 90 degrees along a surface of
the first plate component and skewed toward the opening of the
second plate component pocket and wherein the second plate
component comprises a prawl for engaging the tooth-like protrusions
of the first plate component, wherein the tooth-like protrusions
and the prawl are dimensioned and configured to allow only
unidirectional relative movement of the first and second plate
components.
8. The bone fixation device of claim 1 wherein the distal end of at
least of the first and second plate components has a lamina
stabilizing flange such that the device can be positioned to be in
contact with an anterior, posterior, superior and inferior surfaces
of a divided lamina functioning to grip a cut edge of the lamina
and aiding in positioning and securing the plate to the lamina.
9. The bone fixation device of claim 1 wherein the lamina
stabilizing flange comprises a claw-like protrusion.
10. The bone fixation device of claim 1 wherein the lamina
stabilizing flange comprises a cuff that surrounds a portion of a
transected lamina.
11. The bone fixation device of claim 1 wherein the lamina
stabilizing flange comprises a cup that completely encloses a
portion of a transected lamina.
12. The bone fixation device of claim 1 further comprising a bone
graft-engaging portion configured to aid in retention of an
allograft along a portion of the length of the allograft when the
allograft is disposed within a surgically created gap a lamina.
13. The bone fixation device of claim 12 wherein the bone
graft-engaging portion comprises a hollow recess disposed within a
surface of the elongated fixation plate.
14. The bone fixation device of claim 12 wherein the hollow recess
is rectangular in shape.
15. The bone fixation device of claim 12 wherein the bone
graft-engaging portion comprises deformable fingers configured to
engage the bone graft.
16. The bone fixation device of claim 6 further comprising a bone
graft-engaging portion in the form of a hollow recess is disposed
within a surface of the second plate component.
17. The bone fixation device of claim 16 further comprising a bone
graft-engaging portion in the form of a hollow recess is disposed
within a surface of the first plate component.
18. The bone fixation device of claim 1 wherein at least a portion
of the device is fabricated from a material comprising titanium or
a titanium alloy.
19. The bone fixation device of claim 1 wherein at least a portion
of the device is fabricated from a material comprising a
polyetheretherketone or a polyaryletherketone.
20. A bone fixation kit for use in the lamina of the spine after
laminoplasty comprising a device of claim 1 and forceps for the
separation of the slidably coupled first and second plate
components wherein the forceps comprise gripping ends that separate
as grasping ends are brought together.
21. A method of providing a desired distance between first and
second cut bone ends produced during a laminoplasty procedure,
comprising the steps of: (a) performing a laminoplasty procedure to
produce a transected lamina; (b) providing a bone fixation device
of claim 1; (c) fixedly attaching the distal end of the first plate
component to a lamina facet on one side of a transected lamina and
fixedly attaching the distal end of the second plate component to a
lamina facet on the side of the transected lamina opposite the side
to which the distal end of the first component is fixedly attached;
(d) slidably adjusting the first plate component and second plate
component to produce a desired overall fixation plate length while
separating the lamina at the transection to created an open space
in the lamina; and (e) utilizing the locking means to fix the
position of the first plate component and second plate component
relative to one another.
22. The method of claim 20 further comprising the step of securing
a bone graft within the open space in the lamina.
Description
RELATED APPLICATION DATA
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Application Ser. No. 61/091,944,
filed Aug. 26, 2008.
FIELD OF THE INVENTION
[0002] The present invention relates to a medical implant for bone
surgery, and more specifically to a vertebral fixation system with
an expandable configuration.
BACKGROUND
[0003] In the spine the spinal cord and nerve roots are surrounded
and protected by the vertebrae, which define an opening called the
spinal canal through which the spinal cord passes. Ligaments and
blood vessels are also present in the spinal canal. Spinal stenosis
is a condition where there is narrowing of the spinal canal and
often the neural foramen that causes compression of the spinal cord
and/or nerve roots. Such a narrowing can be caused by numerous
factors including bone spurs, degeneration of the intervertebral
disks and facet joints, and thickening of the ligaments. Among the
symptoms spinal stenosis can produce are pain and/or numbness in
the arms, clumsiness of the hands, and gait disturbances.
[0004] Two surgical methods currently exist to create additional
room in the spinal canal to decompress the spinal cord. The first
is called a laminectomy, which involves removal of the lamina
(roof) of one or more vertebrae. A limitation of the laminectomy
procedure is that it involves removal of the supporting structures
at the back of the vertebrae, which align the spinal column. The
result may be that a patient suffers some postural deformity. To
prevent such postural problems, a graft may be installed between
the ends of the removed bone to span the void and reinstate the
necessary support.
[0005] The second procedure is called a laminoplasty, in which the
targeted vertebra is cut, spread apart and a laminoplasty plate is
attached to bridge the hinged opening in the lamina. Normally a
plate of an appropriate size is selected and bent to the desired
shape and is fastened to the vertebra utilizing a plurality of
screw holes. A strut of bone allograft can be inserted to
permanently enlarge the space. Unlike the laminectomy, typically no
structural bone material is excised during the laminoplasty
procedure.
[0006] Two different laminoplasty procedures are in current use.
The first is called the unilateral or "open door" laminoplasty in
which one side (lamina) of the vertebra is cut all the way through,
while the other side of the vertebra is cut only half-way through
to create a hinge. The vertebral element is then rotated about the
hinge, and the graft is inserted into the opening, increasing the
opening of the spinal canal. The second procedure is called the
bilateral or "French door" laminoplasty in which the midline of the
vertebra (spinous process) is cut all the way through, and the
lamina are cut half way through, creating two hinges. The vertebral
element is then opened at the bisected spinous process, and a graft
inserted into the opening, again increasing the opening of the
spinal canal. Such laminoplasty procedures relieve pressure on the
spinal cord while maintaining the stabilizing effects of the
posterior elements of the vertebrae.
[0007] During a cervical "open door laminoplasty", an incision is
made on the back of the neck and a groove is cut down one side of
the cervical vertebrae, creating a hinge. The other sides of the
vertebrae are cut all the way through. At this point the spinous
process is removed to allow the lamina bone flap to be swung open.
A laminoplasty plate is then screwed to a facet and to the hinged
open lamina. A plate of an appropriate size is selected and bent to
the desired shape and preferably has a plurality of screw holes. A
strut or wedge of bone can be placed in the open portion within the
lamina and the facet to help hold the open position of the lamina.
At the end of the procedure, the door of the vertebrae closes,
wherein the laminoplasty plate and bone wedges prevent it from
closing completely and the spinal cord and the nerve roots rest
comfortably behind the door. By relieving pressure on the spinal
cord it is the goal of laminoplasty to stop the progression of
damage to the spinal cord and allow for as much recovery of
function as possible.
[0008] A notable problem with such a laminoplasty procedure is that
prior to performing such a procedure, the surgeon must measure the
vertebra to determine the dimensions of the plate necessary for
implantation. A laminoplasty implant is needed that allows its
length to be varied during implantation while simultaneously
distracting (opening) the surgically created gap in the lamina.
Additionally such an expandable plate allows its length to be
varied without changing its overall shape or configuration, so that
a plate need not be selected and intensively custom shaped and
formed prior to each surgery.
[0009] Various laminoplasty implants are known in the art. For
example, U.S. Pat. No. 5,980,572 to Kim et al. and U.S. Pat. No.
6,080,157 to Cathro et al. each describes fixed-size implant
designed to stabilize the lamina after open door or double door
laminoplasty procedures. However such devices must be custom
selected and intensively shaped and formed prior to each surgery
and adjustment of the gap or space formed in a lamina after
implantation is not possible. Another limitation of these implants
and associated techniques is that a single implant extends to all
the laminoplasty levels and does not provide well for lamina
fusion, thereby being susceptible to stress fatigue.
[0010] U.S. Pat. No. 6,635,087 to Angelucci et al. describes
implants for use in unilateral and bilateral laminoplasty
procedures, wherein an implant of fixed length is installed between
the cut segments of a transected vertebra and wherein the spinal
canal is expanded. The implant is essentially a plate having ends
that fasten to opposing segments of the transected vertebra and
also has an intermediate portion configured to receive and hold a
portion of bone allograft material. While such a device does
provide for a level of lamina fusion it does requires custom
selection and shaping prior to each surgery and adjustment of the
gap or space formed in a lamina after implantation is not
possible.
[0011] U.S. Pat. No. 6,660,007 to Khanna also describes fixation
devices of fixed length for stabilization and fusion of vertebral
laminae after laminoplasty procedures. These devices consist of a
plate contoured at each end and of a length, width and thickness
specific for vertebrae of the cervical, thoracic or lumbar spine
and also have an intermediate portion configured to receive and
hold a portion of bone allograft material. While such a device does
provide for a level of lamina fusion it does requires custom
selection and shaping prior to each surgery and adjustment of the
gap or space formed in a lamina after implantation is not
possible.
[0012] U.S. Pat. No. 7,264,620 to Taylor relates to an implant
having first and second bases configured for securing two first and
second cut portions, respectively, of a transected vertebra;
wherein a connecting member can be configured for associating the
first and second bases at a pre-selected spacing from each other.
However, with such a device the spacing must be chosen prior to
fixedly attaching the first and second bases to the two first and
second cut portions of the vertebral laminae and adjustment of the
spacing after attachment is not possible.
[0013] Therefore, there exists a need for an implant for use in
either the open door or double door laminoplasty procedures is that
allows the size to be varied after fixation to the laminae without
changing the overall shape or configuration.
[0014] Also, there exists a need for an implant use in either the
open door or double door laminoplasty procedures wherein the
implant not have to be custom selected and intensively shaped and
formed prior to each surgery.
[0015] Furthermore, there exists a need for an implant or use in
either the open door or double door laminoplasty procedures wherein
the implant is configured such it can be used to expand the gap or
opening in the transected lamina to a precisely desired distance
after the implant has been fixedly attached.
[0016] The implant devices of the present invention address these
and other needs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 depicts an isometric view of a bone fixation device
of the invention attached to a lamina in the final position
following a laminoplasty procedure.
[0018] FIG. 2 depicts an isometric view of an expandable lamina
fixation device in a relatively closed or contracted position along
with device-expanding forceps.
[0019] FIG. 3 depicts an isometric view of expandable lamina
fixation device in a relatively open or expanded position along
with device-expanding forceps.
[0020] FIG. 4 depicts an isometric view of an expandable bone plate
50 in an expanded or open position.
[0021] FIG. 5A depicts an orthographic top view of an expandable
bone plate assembly provided with a ratchet mechanism.
[0022] FIG. 5B depicts an orthographic side view of the expandable
bone plate assembly of FIG. 5A.
[0023] FIG. 5C depicts an isometric view of the bone plate assembly
of FIG. 5A.
[0024] FIG. 6A is an orthogonal top view of an embodiment of an
expandable bone plate.
[0025] FIG. 6B an orthogonal cut sectional end view of the
expandable bone plate of FIG. 6A.
[0026] FIG. 7A is an orthogonal top view of an embodiment of an
expandable bone plate.
[0027] FIG. 7B an orthogonal cut sectional end view of the
expandable bone plate of FIG. 7A.
[0028] FIG. 8A is an orthogonal top view of an embodiment of an
expandable bone plate.
[0029] FIG. 8B is an orthogonal bottom view of an embodiment of an
expandable bone plate of FIG. 8A.
[0030] FIG. 8C an orthogonal cut sectional end view of the
expandable bone plate of FIGS. 8A and 8B.
SUMMARY OF THE INVENTION
[0031] The present invention describes an expandable and
distractible implant that is used for stabilization of a lamina
after an open door or double door laminoplasty procedure. Such a
device offers controlled opening of a space within the lamina along
with integrated fixation. In a typical laminoplasty procedure a
lamina is first completely transected near the junction of the
lateral mass and then a hinge is created on the contralateral side
by scoring approximately half the thickness of the lamina. The
transected lamina is expanded to create a laminar gap, a bone
allograft is inserted into the gap and a gap-bridging plate is
fastened at each side of the gap to stabilize the lamina. In
preferred embodiments of the present invention the plate is
comprised of two separate components, namely an inner component and
an outer component. The plate is configured such that the proximal
end the inner component is disposed within the proximal end of the
outer component such that the inner and outer components are
slidably coupled thus allowing the overall length of the assembled
plate to be conveniently adjusted and locked into the desired
position. Additionally, such an embodiment is useful for
conveniently distracting (expanding) the lamina after the lamina
has been surgically transected. In a typical use the distal end of
either the inner or outer component is fixedly attached to the
lamina on one side of the transection and the distal end of the
other component is fixedly attached to the lamina on the opposing
side of the transection and the components are then slidably
adjusted to a desired overall plate length while separating the
lamina at the transection to created a open space or gap in the
lamina. In certain preferred embodiments the distal end of each of
the two plate components comprises one or more holes through which
a bone screw can be inserted to fixedly attach the elements to the
lamina. Also in certain preferred embodiments the expandable plate
also comprises a means for locking the two components of the plate
into the desired relative positions position. Such a locking means
can be, but is not limited to, a setscrew type mechanism. The
expandable laminoplasty plates of the present invention are useful
in open door (unilateral), double door (bilateral) and extensive
laminoplasty procedures. In certain preferred embodiments the plate
assembly is provided with a ratchet mechanism that allows the plate
to be expanded (lengthened) along the longitudinal axis while
preventing the plate from returning to a shortened position.
[0032] A typical bone fixation device of the present for use in the
he lamina of the spine after laminoplasty comprises: an elongated
fixation plate having adjustable length comprising a first plate
component having a distal end, a proximal end and a longitudinal
axis extending there between; said first plate component being
slidebly coupled to a second plate component having a distal end, a
proximal end and a longitudinal axis extending there between;
wherein the distal end of the first plate component is configured
to be fixedly attachable to a lamina facet on one side of a
transected lamina and wherein the distal end of the second plate
component is configured to be fixedly attachable to a lamina facet
on the side of the transected lamina opposite the side to which the
distal end of the first component is fixedly attachable; wherein
the first plate component and second plate component can be
slidably adjusted to produce a desired overall fixation plate
length while the distal ends of the first and second plate
components are each fixedly attached to opposing facets of the
transected lamina and the two plate components are the locked
relative to one another in the desired positions; and a locking
means to secure the position of the first plate component and
second plate component relative to one another.
[0033] In certain preferred embodiments the proximal end of the
first plate component is slidably coupled within a pocket in the
proximal end of the second plate component.
[0034] In certain embodiments the distal end of the first plate
component and the distal end of the second plate component each
have one or more bone screw receiving holes configured to permit
fixed attachment to lamina facets with standard bone screws. Such
bone screw receiving holes can assume any suitable shape such as
round or elongate slots.
[0035] In certain preferred embodiments the locking means is a
setscrew while in other preferred embodiments locking means is a
ratchet mechanism. In certain embodiments, wherein the proximal end
of the first plate component is slidably coupled within a pocket in
the proximal end of the second plate component, the locking means
is a ratchet mechanism comprising a series of tooth-like
protrusions set an angle less of than 90 degrees along a surface of
a first plate component and skewed toward the opening of a second
plate component pocket and wherein the second plate component
comprises a prawl for engaging the tooth-like protrusions of the
first plate component, wherein the tooth-like protrusions and the
prawl are dimensioned and configured to allow only unidirectional
relative movement of the first and second plate components.
[0036] In certain embodiments the distal end of at least of the
first and second plate components has a lamina stabilizing flange
such that the device can be positioned to be in contact with an
anterior, posterior, superior and inferior surfaces of a divided
lamina functioning to grip a cut edge of the lamina and aiding in
positioning and securing the plate to the lamina. In certain
preferred embodiments the lamina-stabilizing flange is in the form
of a claw-like protrusion, while in other embodiments the
lamina-stabilizing flange comprises a cuff that surrounds a portion
of a transected lamina. In still other embodiments the
lamina-stabilizing flange comprises a cup that completely encloses
a portion of a transected lamina.
[0037] Certain embodiments of the bone fixation devices of the
present invention have a bone graft-engaging portion configured to
aid in the retention of an bone graft or allograft along a portion
of the length of the graft when the graft is disposed within a
surgically created gap a lamina. In certain embodiments the bone
graft-engaging portion is a hollow recess disposed within a surface
of the elongated fixation plate. In certain embodiments the bone
graft-engaging portion in the form of a hollow recess disposed
within a surface of either the first plate component, second plate
component or both plate components. Such hollows or recesses can
assume a variety of configurations and geometrical shapes
including, but not limited to, round, ovoid, polygonal such as
triangular or rectangular, and the like. In certain other
embodiments the bone graft-engaging portion comprises deformable
fingers or finger-like protrusions, which can be readily configured
to engage the bone graft.
[0038] In certain embodiments the device the slidably coupled first
and second plate components can be conveniently separated by
utilizing forceps designed such that the gripping ends separate as
the grasping ends are brought together.
[0039] The present invention also relates to methods of providing a
desired distance between first and second cut bone ends produced
during a laminoplasty procedure. A typical method comprises the
steps of: (a) performing a laminoplasty procedure to produce a
transected lamina; (b) providing a bone fixation device as herein
described; (c) fixedly attaching the distal end of the first plate
component to a lamina facet on one side of a transected lamina and
fixedly attaching the distal end of the second plate component to a
lamina facet on the side of the transected lamina opposite the side
to which the distal end of the first component is fixedly attached;
(d) slidably adjusting the first plate component and second plate
component to produce a desired overall fixation plate length while
separating the lamina at the transection to created an open space
in the lamina; and (e) utilizing the locking means to fix the
position of the first plate component and second plate component
relative to one another. In certain embodiments such a method
further comprises the step of securing a bone graft within the open
space in the lamina.
DETAILED DESCRIPTION OF THE INVENTION
[0040] The present invention describes embodiments of an expandable
implantable plate that is used for stabilization of a lamina in a
laminoplasty procedure wherein the plate offers controlled opening
of a space within a transected lamina with integrated fixation. In
preferred embodiments the plate is comprised of a first plate
component slidably coupled to a second plate component. In a
typical laminoplasty procedure a lamina is first completely
transected near the junction of the lateral mass and then a notch,
often also referred to as a hinge, is created on the contralateral
side the lateral mass. In a laminoplasty procedure utilizing an
expandable plate of the present invention the distal end of either
the first plate component or second plate component is fixedly
attached to the lamina on one side of the transection and the
distal end of the other component is fixedly attached to the lamina
on the opposing side of the transection. The first plate component
and the second plate component are then slidably adjusted to a
desired overall plate length to expand the lamina at the
transection thereby creating an open space or gap. Finally, the two
plate components are the locked relative to one another in the
desired positions.
[0041] In typical embodiments, the devices have one or more bone
screw receiving holes at the distal ends of the first plate
component and the second plate component, which permits fixed
attachment to lamina facets with standard bone screws. Such bone
screw receiving holes can assume any suitable shape such as round
or elongate slots.
[0042] The locking of the position of a first plate component
relative a second plate component can be achieved by a variety of
means including, but not limited to, bolts, set screws, clamps,
clips and the like. In certain preferred embodiments, wherein a
first plate component is slidably coupled and disposed within a
pocket of a second plate component, locking is achieved by
incorporation of a ratchet mechanism. Such a mechanism consists of
tooth-like protrusions are set any acute angle of less than 90
degrees, preferably of less than 60 degrees and more preferably
less than 45 degrees, along the surface of the first plate
component and are skewed toward the opening of the second plate
component pocket and the second plate component comprises a prawl
for engaging the tooth-like protrusions of the first plate
component, wherein the tooth-like protrusions and the prawl are
dimensioned and configured to permit only unidirectional relative
movement of the first and second plate components when the engaging
flat (opposite face of teeth and prawl) surfaces of the are
coplanar. The ratchet mechanism as herein described is intended to
be exemplary and it is understood that variations of this and other
ratchet mechanisms will be apparent to one skilled the art.
[0043] In certain other preferred embodiments the distal end of at
least of the first and second plate components has a lamina
stabilizing flange which can be positioned to be in contact with an
anterior, posterior, superior and inferior surfaces of a divided
lamina functioning to grip a cut edge of the lamina and aiding in
positioning and securing the plate to the lamina. Suitable
stabilizing flanges can be configured in a variety of forms
including, but not limited to, a claw-like protrusion that engages
an edge of a divided lamina, a cuff that substantially surrounds a
portion of a divided lamina and a cup that completely encloses the
first portion of the divided lamina. Suitable stabilizing flanges
are those described in the published US Pat. Appl. US 2004/0030388
to Null et al., which is being included herein in its entirety by
way of reference.
[0044] In certain laminoplasty procedures a bone or bone generating
material of either a biologic or non-biologic nature is inserted
into the gap. For use in such procedures embodiments of the
expandable laminoplasty plates of the present invention are
provided with a recess, a graft window or similar feature to assist
in placement and/or retention of such bone generating material. A
suitable configuration for such a bone graft retaining recesses or
windows is disclosed in U.S. Pat. No. 6,635,087 to Angelucci et
al., which is being included herein in its entirety by way of
reference. Another suitable configuration for a bone graft or bone
generating material retention is the configuration of the
fixed-length as NewBridge.TM. Laminoplasty Fixation System
available from Orthofix Spinal Implants, McKinney, Tex. USA. A list
of appropriate bone or bone generating material for use in these
embodiments includes, but is not limited to allografts such as
fresh bone, freshly frozen bone, freeze-dried bone allograft
(FDBA), demineralized freeze-dried bone allograft (DFDBA),
demineralized bone matrix (DBM) containing bone morphogenetic
protein (BMP), ceramics, calcium phosphates such as hydroxyapatite
or tricalcium phosphate and the like.
[0045] In situ expansion of the embodiments of an expandable
laminoplasty plate of the present invention during a laminoplasty
procedure can be achieved by a variety of means including, but not
limited to, manual separation of the slidably coupled first and
second plate components and use of various surgical tools or
instruments. In certain preferred embodiments separation of the
slidably coupled first and second plate components is conveniently
achieved by the use of forceps designed such that the gripping ends
separate as the grasping ends are brought together.
[0046] An embodiment of the invention attached to a lamina in the
final position after a laminoplasty procedure is illustrated in
FIG. 1 wherein a lamina 20 has been transected near the junction of
the lateral mass 21 and a hinge 22 has been created on the
contralateral side. The bone fixation device 10 comprises a second
plate component 11 the proximal end of which is essentially a flat
plate slidably coupled within a pocket formed within the proximal
end of the first plate component 12, wherein the distal end of the
second plate component 11 is fixedly attached to a facet of the
lamina by a bone screw 15 while the distal end of the first plate
component 12 is fixedly attached to a facet of the lamina by a bone
screw 16 and the second plate component 11 is fixedly attached to a
facet of the lamina by a bone screw 16. Since the second plate
component 11 and first plate component 12 are slidably coupled, the
length of the plate is conveniently adjusted to a desired length
thereby expanding the gap 23 in the lamina 20 to a desired
dimension. An optional locking means for fixing the relative
positions of the second plate component 11 and first plate
component 12 is depicted in FIG. 1 as setscrew 17. Also in the
embodiment illustrated in FIG. 1 a bone allograft 24 has been
inserted within the gap 23.
[0047] Another embodiment of the invention is illustrated in FIG. 2
wherein an expandable lamina fixation device 30 is depicted in a
relatively closed or contracted position along with
device-expanding forceps 40. The expandable fixation device 30
comprises and second plate component 31 slidably coupled and
disposed within a pocket within a first plate component 32. In this
embodiment the second plate component 31 comprises part of a
ratchet mechanism in the form of tooth-like protrusions 35 set an
acute angle such to be skewed toward the opening in the first plate
component 32 and the first plate component 32 comprises a prawl 36
for engaging tooth-like protrusions 35, wherein the tooth-like
ratchet components 35 and the prawl 36 are dimensioned and
configured to allow only unidirectional relative movement of the
first plate component 31 and the second plate component 32 when the
engaging flat (opposite face of teeth and prawl) surfaces of the
elements are coplanar. An additional feature of this embodiment is
the claw-like protrusion 33 positioned near the distal end of first
plate component 31 and which functions to grip a cut edge of a
lamina and aids in positioning and securing the device 30 to a
lamina. In FIG. 3 is illustrated the same expandable lamina
fixation device depicted in FIG. 2, wherein the lamina fixation
device 30 is in an expanded or open position along with
plate-expanding forceps 40. This illustration clearly depicts the
ratchet teeth 35 disposed along a surface of first plate component
31 as well as the prawl 36 disposed within the opening second plate
component 32. FIG. 3 also clearly depicts bone screw receiving
holes 37 and 38 at the distal ends of components 32 and 31
respectively wherein the holes are sized to accept standard bone
screws 39. In use, the lengthening of the device 30 the positioning
of the first plate component 31 and second plate component 32
relative to one another along the longitudinal axis effects
distraction of a lamina (i.e. expanding the space in a lamina) to
create a gap and further stabilizes the distracted lamina.
[0048] Another embodiment of the present invention is illustrated
by FIG. 4 depicting an expandable bone plate 50 in an expanded or
open position. The plate 50 comprises a first or inner plate
component 51 slidably disposed within a second or outer plate
component 52. The first plate component 51 further comprises a
lamina stabilizing flange 53 in the form of a claw-like protrusion
positioned near the distal end of inner component 51 and which
functions to grip a cut edge of a lamina and aids in positioning
and securing the bone plate 50 to the lamina. The expandable bone
plate 50 also comprises screw-receiving holes 54 and 55 at the
distal ends of components 52 and 51 respectively wherein the holes
are sized to accept bone screws 56. The expandable bone plate 50
also comprises a set screw 57 that functions as a locking mechanism
to secure the position of inner component 51 and outer component 52
relative to one another.
[0049] FIGS. 5A, 5B and 5C depict an expandable bone plate assembly
60 provided with a ratchet mechanism that allows the plate to be
expanded (lengthened) along the longitudinal axis while preventing
the plate from returning too a shortened position. FIG A is an
orthogonal top view of a disengaged inner component 61 and outer
component 62; FIG. 5b is an orthogonal side view of disengaged
inner component 61 and outer component 62; and FIG. 5c is an
isometric view of inner component 61 and outer component 62 when
engaged. In this embodiment the inner component 61 comprises a
series of linear ratchet components 65 in the form of tooth-like
protrusions set an acute angle such that they are skewed toward a
pocket-like opening the outer element 61 and the outer element 61
comprises a prawl 66 for engaging ratchet components 65, wherein
the ratchet components 65 and the prawl 66 are dimensioned and
configured to allow only unidirectional relative movement of the
inner element 61 and the outer element 62 when the engaging flat
(opposite face of teeth and prawl) surfaces of the elements are
coplanar. Effectively when the engaging surfaces of the elements
are coplanar which limits the plate to expansion of the length.
However, in certain embodiments the ratchet mechanism is
dimensioned and configured such that a ratcheted plate can be
restored to a contracted or closed position by adjusting the
orientation of the elements to one another. Another feature of the
embodiment depicted in FIG. 5 is the lamina stabilizing flange 69
which can be positioned to be in contact with an anterior,
posterior, superior and inferior surfaces of a divided lamina.
Round screw-receiving holes 67 and 68 are also depicted.
[0050] In FIG. 6A is illustrated an orthogonal top view of an
embodiment of an expandable bone plate 70 and in FIG. 6B a is
illustrated cut sectional end view of the same expandable bone
plate 70, wherein an first or inner component 71 is slidably
disposed in pocket within second or outer component 72. The cut
sectional view FIG. 6B clearly shows the inner component 71
disposed within a fully closed pocket or envelope in outer
component 72. Round screw-receiving holes 73 are also depicted in
FIG. 6A
[0051] In FIG. 7A is illustrated an orthogonal top view of an
embodiment of an expandable bone plate 80 and in FIG. &B a is
illustrated cut sectional end view of the same expandable bone
plate 80 wherein an inner component 81 is slidably disposed within
an outer component 82 and wherein the plate comprises a set-screw
locking mechanism 83. The cut sectional view 7B clearly shows the
inner component 81 disposed and maintained within a partially
closed pocket or envelope in outer component 82 and wherein the
inner component is locked in place with the outer component by the
pressure exerted against the inner component 81 by the setscrew 83.
Furthermore in this embodiment the partial opening 85 in the pocket
outer component 82 provides a recess that is a suitable bone
graft-engaging portion of the expandable bone plate 80. Round
screw-receiving holes 84 are also depicted in FIG. 7A.
[0052] In FIG. 8A is illustrated an orthogonal bottom view of an
embodiment of an expandable bone plate 90, in FIG. 8B an orthogonal
top view of the expandable bone plate 90 and in FIG. 8B is
illustrated cut sectional end view of the same expandable bone
plate 90 wherein an inner component 92 is slidably disposed within
an outer component 91 and wherein the plate comprises a set-screw
locking mechanism 95. In this embodiment the inner component 92 has
a rectangular recess 94 configured to provide a bone graft-engaging
portion of the expandable bone plate 90 and wherein a partial
opening 93 in the pocket of the outer component 91 forms an
additional rectangular recess to act as bone graft-engaging
feature.
[0053] It should be understood that certain features of the
expandable bone plate fixation system configurations depicted in
the accompanying figures are for illustrative purposes and that
many variations are possible and in certain embodiments necessary.
For example, there is no limitation with respect the angles formed
between the ends of the plate and the major plate body which can be
anywhere in the range of 0.degree. to 90.degree. and is chosen to
conform to the geometry as dictated by the surgical procedure.
[0054] Materials useful for fabrication of embodiments of the
implants of the present invention include any bio-compatible
material having sufficient strength to maintain the open position
of the divided lamina. Examples of suitable materials include, but
are not limited to, titanium, titanium alloys, ceramics,
composites, plastic composites, PEEK (polyetheretherketone) or PAEK
(polyaryletherketone) as well as bioresorbable materials such as
polylactides, polyglycolides and copolymers and blends thereof. The
laminoplasty plates can also be constructed of a material that is
radiolucent and/or bone growth inducing. In certain specific
embodiments, a particularly suitable material is the titanium alloy
designated as CP Ti grade 2 alloy.
[0055] Other embodiments of the devices and methods of the present
invention will become apparent to those skilled in the art based on
the description and drawings of the embodiments presented herein
and the present invention is in no way limited to these
embodiments.
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